This invention relates to vehicle headliners and a method of forming vehicle headliners, and more particularly to vehicle headliners comprising a plurality of thermoformable layers which are compressed and molded to form a laminate having a predetermined contoured shape.
Many vehicle headliners have been constructed utilizing resin impregnated glass fiber. A resin impregnated glass fiber batt is compression molded into the desired headliner shape, and the resin is cured to maintain the molded shape. A thin layer of foam, such as polyurethane, overlies the molded fiberglass shape, and fabric is attached to the foam to form the exposed interior surface of the headliner. Because the glass fiber reinforced layer of such headliners is a rigid, often impermeable layer, it tends to reflect sound. Accordingly, undesirable ambient noises, including noise from the engine compartment or drive train, which enter the cabin are not absorbed by the headliner, but instead are reflected back into the cabin by the fiber reinforced resin layer.
Another type of vehicle headliner is prepared by thermoforming a laminate comprised of a stiff structural, yet thermoformable polystyrene foam layer and layers of kraft paper or a polymer film material bonded to either side of the foam. This laminate is covered with a soft foam backed fabric. Such headliners do not have sufficiently desirable sound absorbing properties because the kraft paper or polymer film tends to reflect sound rather than absorb sound.
A sound absorbing laminate which is useful for forming three-dimensionally contoured articles such as automobile headliners, and which exhibits substantially improved sound absorbing properties, is disclosed in U.S. Pat. No. 5,068,001, the rights of which have been assigned to Prince Corporation, Holland, Mich., the Assignee of the present invention. The laminate is comprised of a resilient, porous fibrous core layer, to which is adhered a fibrous, porous reinforcing mat to give the composite strength. The three-dimensional sound absorbing structure is generally formed by providing a first reinforcing porous, fibrous mat, providing a core defined by a resilient thermoformable porous fiber batt having a thickness of at least about 1/4 inch, laminating the mat to one surface of the batt by impregnating the mat and its interface with the batt with sufficient binder resin to effect adherence therebetween, but insufficient resin binder to form a porosity-blocking film, and thermoforming the laminate into a porous three-dimensional configuration. While the sound absorbing laminate described in U.S. Pat. No. 5,068,001 provides substantially improved sound absorbing properties as compared with other known vehicle headliner constructions, vehicle manufacturers desire even better sound absorbing properties, and in particular desire headliner constructions which are capable of exhibiting excellent sound absorbing properties for particular frequency ranges depending on the characteristics of the vehicle. Also, while the method described in U.S. Pat. No. 5,068,001 is useful for mass producing automobile headliners on automated equipment, the amount of time which the laminate must remain in either a thermoforming molding tool or placed in a cooling fixture having a shape substantially identical with that of the molding tool, in order to form a high quality headliner in the desired three-dimensionally contoured configuration, can be more than is desirable.